CRYSTAL TO NON EQUILIBRIUM PHASE TRANSITION INDUCED BY BALL-MILLING IN SILICON AND THE IMMISCIBLE Si(Sn, Zn) SYSTEMS

Resume- La formation de phases metastables- systhme pur Si, systhmes non miscibles SiSn, SiZn- (soient: phases amorphes, solutions solides crystallines sursaturees etlou composes metastables) par chocs mecaniques (broyage) a et6 mise en evidence par diffraction de RX, des observations par MEB, des analyses chimiques EDX/MEB et enfin la stabilite thermique de ces phases a et6 Btudiee par calorim6trie differentielle B balayage. L'obtention de ces phases indique qu'une reaction de melange negative n'est pas une condition necessaire pour la formation d'amorphe sous broyage: le mecanisme de transition de phase doit &re distinct de celui mis en jeu lors de l'amorphisation par diffusion de multicouches. Abstract- Based on XRD patterns, SEM observations, EDXISEM analyses and DSc experiments, we report on the crystal to metastable phase (i.e. amorphous phases, supersaturated crystalline solid solutions andlor non equilibrium compounds) transition induced by ball- milling in a pure element- a Si powder and in two immiscible binary alloys- SiISn and SiIZn. The observations of such dynamic phase equilibria support the idea that a negative heat of mixing is not a necessary condition for the ball- milling amorphisation: the phase transition mechanism which is induced during ball- milling is different by solid state diffusion of multilayered films